Conventional phase shifters in coaxial piping technology are usually realized in the form of so-called trombones. Conduits of pipes of different diameter are displaced against one another, which means that the change of the electric length is achieved directly by changing the mechanical length of the line system. The diameter ratios (Ø of outer conductor to Ø inner conductor) of the individual conduits of pipes which can be displaced against one another are of the same size in the classic trombone, which means that the characteristic impedance has the same magnitude in all sections (so-called compensation according to Weisfloch). No mismatching thus occurs in a change of the mechanical length and thus the electrical length.
It is planned in the International Thermonuclear Experimental Reactor (ITER) fusion experiment to transfer continuous power in the magnitude of 2 MW via coaxial piping systems for the on cyclotron resonance heating (ICRH) in the frequency range of 40 to 55 MHz. It is therefore necessary to cool the inner conductor as well as the outer conductor of all components (e.g., with water). Water-cooled phase shifters are required for the matching networks.